In dynamic applications requiring sealing at low-to-moderate speeds and pressures, design engineers are replacing underperforming elastomeric O-rings with spring-energized PTFE “C-ring” seals.
David Wang, Bal Seal Engineering
When O-rings and other traditional sealing methods fail, diagnostic and drug-delivery equipment engineers are embracing a new and more cost-effective way to improve the performance of their existing hardware designs: The spring-energized PTFE “C-ring” seal.
The challenge: replacing a failed O-ring
The C-ring seal was first developed for a diagnostic tool employing a piston operating in a water bath of approximately 100°F, reciprocating at a rate of 5 feet per minute. The operating conditions were mild, but the tolerances were large. The original design called for an elastomeric O-ring to seal the piston, but the O-ring was unable to maintain a consistent seal and the equipment leaked.
With prototypes already built, engineers began looking for an alternative. U-cups or standard lip seals, which would typically be used in a piston application, were not a viable option because of large radial tolerances. Also, installing these over a full-step groove wasn’t practical. The installation would require too much stretching, resulting in seal deformation and premature failure.